Mohtaram gujar96 Sahib,
I am a pilot with a CFI certification. I do flying out of passion. We guys know how to fly these machines. Modern jets are so high tech that the probability of them crashing because of a technology failure is very minimal.
You are right that pilot error is a major cause of crashes these days, it has to be there if a commercial jetliner were to come down because the chance of technology failing is almost down to zilch.
You are suggesting that the autopilot disengaged and the 777 went into the ocean. Even if the autopilot were to disengage, there are relevant procedures which have to be followed and the plane has to be flown manually and it has to be done. At 35000 feet with the 777 flying around 500 knots it is quite a bit of a challenge to fly the beast manually, but it can be done. The pilots are there in the cockpit to do the job in the event the autopilot disengages.
Autopilot is just there to assist the flying crew and can be disengaged at any time at their discretion. So just forget about the element of the autopilot disengaging and becoming a cause of a crash of a modern commercial jetliner.
Regards.